In vehicles such as, for example, automobiles, it is common to employ an automatic transmission. The transmission is capable of being placed in either a "Park" mode or various non-"Park" modes by manual actuation of a shift control mechanism. The non-Park modes typically include "Reverse," "Neutral," "Drive," "Second" and "First."
The shift control mechanism typically includes a shift lever which is either floor mounted or may be column mounted on the steering column. In most such shift control mechanisms there is provided a detent mechanism, which interacts with the shift lever to aid in maintaining it in a selected position associated with a selected transmission mode.
Many such automatic transmission shift control mechanisms include provision for locking the shift lever in the Park detent position, while the ignition switch is in the "Off" position. This aids in theft prevention. An example of such an arrangement is presented in U.S. Pat. No. 4,474,085 (issued Oct. 2, 1984 to DeVogelaere et al), in which a pivotable shift lever has a pushbutton operated, detent mechanism which is operatively connected with a "Park/Lock" lever pivotally mounted on the shift control mechanism. The Park/Lock lever is controlled by actuation of the vehicle ignition lock.
Still further, where there is some concern that a gear shift lever might inadvertently be left in a pseudo-park position, which would allow dislodgement by shock or vibration, possibly into Reverse, provision has been made to insure that the detent pin does find its way into the actual Park detent slot, rather than to dwell at some unacceptable intermediate position.
Such an arrangement is depicted and disclosed in U.S. Pat. No. 4,473,141 (issued Sept. 25, 1984 to Mochida), in which a plunger actuated by an electromagnet acts, when not energized, to insure proper final positioning and retention of the detent pin in the Park position. When the electromagnet is energized, the plunger retracts and the detent pin is freed to allow actuation of the gear shift lever. The electromagnet is connected in series with a park brake switch and the ignition switch such that, when the engine is running and the park brake is actuated, the plunger retracts.
More recently, a concern has developed regarding a condition termed "sudden acceleration," in which the vehicle may lurch forward or backward when the gear shift lever is moved from Park to one of the non-Park positions such as Reverse or Drive. One technique for minimizing or preventing problem acceleration is to require that the brakes be applied while shifting out of the Park position.
While this may normally be good operating practice, it is preferable to provide an interlock, which effectively requires that response. One such brake/shift interlock of which Applicants are aware requires, in addition to the existing shift control mechanism having a key-actuated interlock cam, or Park/Lock member, (hereinafter "P/L" member), a further brake interlock cam for blocking the P/L member, a solenoid having a plunger and rigid arm extensible to actuate the brake interlock cam into actuating engagement with the P/L member when the ignition switch is in the "Run" position and being deactivated when the vehicle's brake is actuated, and a switch for detecting when the shift control mechanism is in the Park position in order to inhibit operation of the solenoid during brake actuation when other than in Park, so as to prevent the noise and wear associated with its actuation.
Accordingly, it is a principal object of the present invention to provide an improved brake/shift interlock for the shift control mechanism associated with the automatic transmission of a vehicle.
It is a further object to provide an improved electromagnetic actuator assembly useful in such brake/shift interlock mechanism.
It is a still further object of the invention to provide such improved brake/shift interlock in combination with the shift control mechanism for an automatic transmission.
As part of the foregoing general objects, it is a further object to provide a reliable brake/shift interlock which may be economically added to an existing shift control mechanism.
It is a further object of the invention to provide an electromagnetic actuator for the brake/shift interlock of a design which permits an economy of functions.
Finally, in comparison to the brake/shift interlock system of the parent case, which likewise had the foregoing objects, it is an additional, primary object of the present invention to further improve the electromagnetic actuator for such a system, particularly in the manufacturing aspects thereof.
With respect to the exemplary solenoid of the parent case, it is noted that the solenoid plunger (62) had to be crimped, staked or otherwise fixedly attached to an actuating cable (44; comparable to the cable 44 hereof). Although a significant advance over the prior art, this approach typically required the cable manufacturer, who was different than the solenoid manufacturer, to attach the solenoid plunger to the cable. This in turn required that the solenoid manufacturer only partially pre-assemble the solenoid and ship the partially assembled solenoid to the cable manufacturer for attaching the cable to the plunger, before the solenoid assembly could then be completed.
This situation also created a tolerancing problem. If the plunger was staked too far toward the shifter, the plunger would not properly seat against the bushing or stop, resulting in a loss of the interlock feature. On the other hand, if the plunger was staked too far toward the column, the cable would not then be able to return, which could result in the driver not being able to remove the key from the ignition switch.
Thus, a further object of the present invention is to overcome these manufacturing and tolerancing problems with respect to the electromagnetic, solenoid actuator for the brake/shift interlock.